POS1150 ULTRASOUND-DETECTED EROSIONS COULD PREDICT THE EFFICACY OF BELIMUMAB IN ARTICULAR SYSTEMIC LUPUS ERYTHEMATOSUS
Authors: G. Orsolini, R. Bixio, F. Mastropaolo, A. Piccinelli, E. Favaro, O. Viapiana, G. Adami, M. Rossini
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Articular involvement (69-95%) in patients with systemic lupus erythematosus (SLE) is traditionally considered non-erosive. SLE arthritis with radiographic erosions with or without rheumatoid factor (RF) and/or anti-citrullinated peptide antibody (ACPA) positivity is often described as "rhupus" and is considered an overlap between SLE and rheumatoid arthritis (RA). While radiographic erosions are shown in about 5-15% of the patients, ultrasound and magnetic resonance imaging could reveal erosions in up to 40% of patients with SLE. <h3>Objectives</h3> The aim of this study is to assess if the presence of ultrasound-detected erosions can predict the efficacy of belimumab, a B lymphocyte simulator (BlyS) inhibitor, in the treatment of SLE-related articular manifestations. <h3>Methods</h3> We performed a spontaneous, monocentric, retrospective, and observational study. We enrolled patients with a diagnosis of SLE according with the 2019 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) criteria with articular involvement treated with belimumab. Patients with ACPA- or RF-positivity, Jaccoud's arthropathy, or radiographic erosions were excluded. We collected laboratory and clinical data from the electronic records. Joint disease activity was assessed at baseline, 3- and 6-months follow-ups (FU) using disease activity score on 28 joints based on C-reactive protein (DAS28-CRP). At baseline, all patients underwent an ultrasound examination of the wrist, metacarpophalangeal, proximal interphalangeal, and metatarsal-phalangeal joints. Erosions were defined according with the outcome measures in rheumatology (OMERACT) definition (at least 1 mm). Student's T-test and Mann-Whitney's U-test were used to assess differences between means and Fisher's exact test to assess differences between proportions. <h3>Results</h3> We enrolled 23 patients (baseline characteristics in Table 1). Seven patients (30.4%) had bone erosions at baseline. They were generally older (61±16.1 vs 46.13±10.7 years, p=0.016), more frequently male (42.8 vs 6.2%, p=0.03), with higher CRP levels (10.29±11.6 vs 2.25±3.1 mg/L, p=0.015), and higher C4 (0.19±0.17 vs 0.1±0.04 g/L, p=0.05) than patients without erosions. DAS28-CRP decreased significantly at 6-months FU (2.95±0.89 vs 2.26±0.48, p=0.01) only in patients without erosions, as shown in Figure 1. The majority of patients (73.9%) achieved remission at 6-months FU (DAS28-CRP criteria), with a significant difference between patients with and without erosions (42.8 vs 87.5%, p=0.045). <h3>Conclusion</h3> The presence of ultrasound-detected erosions could be predictive of a decreased efficacy of belimumab in articular SLE. A possible explanation is a rheumatoid-like articular phenotype, despite the lack of ACPA-positivity and radiologic erosions. Our findings could help expand the "rhupus" spectrum and highlight the possible role of different SLE phenotypes in the therapeutic response. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Giovanni Orsolini Speakers bureau: GSK, novartis, amgen, Consultant of: GSK, astrazeneca, Amgen, Riccardo Bixio: None declared, Francesca Mastropaolo: None declared, Anna Piccinelli: None declared, Eleonora Favaro: None declared, Ombretta Viapiana: None declared, Giovanni Adami: None declared, Maurizio Rossini: None declared.